The present invention relates to a method and a device for determining properties, and in particular optical properties, of textured surfaces. Methods and devices of this type have been known from the prior art for a long time. The invention is described with reference to the surfaces of bodyworks, in particular for vehicles, but it is pointed out that the device according to the invention can also be used in the case of other applications, such as for example in the case of floor coverings, in the case of pieces of furniture, and the like. The textured surface is thus characterized by a topography which as well as a lateral extension also has a vertical profile. The human eye, however, cannot evaluate such differences in height in the micrometer range quantitatively but only observes the effects of this texture. However, the invention is not restricted to the investigation of textured surfaces.
Methods and devices of this type which are known from the prior art usually determine specified properties of the surface, such as for example a colour. In this case these devices are used to derive an objective image of the respective surface. Instruments according to the invention are used in particular in the field of quality assurance, in particular if differences have to be ascertained between two surfaces to be compared. In this case too, however, it is not so much the difference existing in terms of quantity which is crucial but rather the human perception.
A method of simulating surface images is known from WO 2008/083206 A3. In this case a data memory is provided which contains a multiplicity of surface colours and a multiplicity of surface textures. In addition, a processor is present which produces an image of a surface in which case it falls back upon a multiplicity of data stored in the data memory.
In many cases, however, it is less relevant to the user to obtain a precise quantitative analysis of a specific surface. It is more relevant in many cases to establish whether for example a substitute lacquer applied to damaged areas corresponds to the lacquer originally applied, in such a way that is not visible to a customer with the naked eye.
The object of the present invention is therefore to make available a method and a device which in particular also permit such a qualitative evaluation of a surface. In addition, a method should be made available which delivers a rapid overview of qualitative properties of these surfaces in as simple a manner as possible.